Electric starter for combustion engines



March 28,1939.

A. s, FISK ELECTRIC STARTER FOR COMBUSTION ENGINES Original Fil ed April 15, 1956 2 'She ts-Sheet l b M w 5 J 1 Nb l .n a. I 3 m N I am in h mm m 18. 6 if mm H mm sgmw QM w a s a w i {I 1.; 8 Es fl .Il Q u mm mm .m w Q an M Q mm 6 ow k v A|. -N mHW v March 28, 1939. A. s. FISK 2,151,962

' ELECTRIC STARTER FOR bOMBUSTION ENGIfiES Original Filed April 15, 19 36 2 Sheets-Sheet 2 INVENTOR @LBERT 6 Han Patented Mar.

-ELECTRIO STARTER FOB conrans'rioN enemas a Albert S. Fisk, Brooklyn, N. Y., assignor to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application April 15, 1936, Serial No.. 74,415

Renewed April 12, 1938 v 8 Claims.

This invention relates particularly to electric starting devices for internal combustion engines,

wherein a jaw clutch of the electric starter is normally disengaged from a cooperating jaw clutch on the engine, but is brought into engagement therewith at the time of starting. In view of the fact that a comparatively small motor is used in starting with a large gear reduction in which lost motion is bound to be present, the mo- 10 tor may speed up to high speed before full engagement of the meshing devices occurs, so that a severe shock of engagement occurs in spite of 25 slip friction clutch between the motor shaft and the aforesaid jaw clutch so that after the jaws engage, said jaws may be driven around through the reduction gear train.

According to my present invention, I do not 30 use the high speed shaft of the starter motor and eliminate the necessity for employing any such slip friction clutches between said shaft and the jaw clutch, with the attendant frictional losses. I employ a separate motive means for effecting 35 quick engagement of the jaws, which, however,

riormally rotates at the same slow speed as the aws.

In my invention I have also improved the construction of the reduction gear between the motor 40 and the jaws, such that no kick back is produced, excessive tooth thrusts are avoided, and higher ratios are obtainablenn a more compact space. This I preferably accomplish by employing a gyrating gear train for this purpose.

My invention ,also has application to other mechanisms having driving and drivenmembers which are automatically engaged and disengaged and wherein it is desirable to take up or prevent back lash or lost motion'prior to the actual shock 50 of engagement.

Referring to the drawings, showing one form my invention may assume,

Fig. 1 is a vertical section of a starter mechanism designed for the starting of aircraft en- 55 zin (o1. zen-as) Fig. 2 is a vertical section taken substantially on line 22 of Fig. 1.

Fig. 3 is a sectional view of the cam or jaw arrangement for advancing the main clutches into engagement, the section being taken through the 5 teeth on the motor shaft, looking toward the engine, v

Fig. 4 is a face view of the one-way clutch connecting the driving jaw and main drive shaft.

In the drawings, the numeral l represents the usual jaw clutch on the end of the engine shaft and 2 the complementary, normally disengaged clutch on the electric starter. The main power drive of the clutch 2 is secured from the starter motor 3 through a reduction gear train. The armature 4 of said motor is shown as mounted on a hollow shaft 5 which is connected to drive an inner shaft 6 through a shear pin 1 which is adapted to shear in case of sudden excessive loads to prevent breakage of other parts. The shaft 6 drives, through a squared or splined end 8, a sleeve 9 journaled for rotation within a rotatable two part frame 'I 0 by means of anti-friction bearings II and [2. The hollow shaft 5 is shown as likewise journaled at its forward end in bearing I3 in said frame l0, and at its rear end in bearing Hi in the motor housing l5.

The sleeve 9 is shown as having pinion teeth It thereon, which drive a plurality of gears l1, l8 and 19. Each of said gears is provided with an eccentric hub 20 which is mounted in antifriction bearing 2| within a hole 22 in a large plate 23 .provided with gear teeth 24 on its outer periphery. The gears l1, l8 and iii are each mounted by means of a long roller bearing 25 on a sleeve 26 secured in said rotatable framework Ill. The two halves of framework 10 may also be fastened together by a plurality'of bolts v2'! and sleeves 50 which pass through holes 5| in gear plate 23. 40

The pitch circle of the gear teeth 24' is somewhat less in diameter than the pitch circle of the internal gear 28 in the fixed housing 29 and has a less number of teeth. In operation, therefore, the pinion It drives the three equally spaced gears II, It and I? at a reduced speed. The three eccentrics 20 thereon given'an eccentric motion to the large gear 23, causing it to gyrate around within the internal gear "and to rotate very slowly on its own axis. The total throw of the eccentric 20 should be equal to the difference in the pitch diameter of the gears 28 and 23 and I the result is that since gear 28 is stationary, gear '23 is advanced that portion of a revolution during each gyration thereof, which is determined by the in use with engine starters, since it is exceptionally compact for the large ratio of 100:1 or more that is required. Space available for engine starters is such as to prohibit the use of the size of starter usually resulting from the adoption of standard gear trains. In the prior art, on many occasions the desired ratio has been reduced in order to keep the size of the starter small enough for practical use.

Also, the direction of rotation of the input shaft 6 and the output sleeve 3| is the same.

This overcomes the disadvantage experienced by other inventors who found it necessary to insert a reverse of direction mechanism.

Also, the gyrating gear train is self locking and only operative from the driving end, so in case of a back fire from the engine there is no kick back and the strain is taken up on the solid eccentrics and the heavy duty gear teeth and not on the light duty gear teeth, as is the case in the prior art.

The framework H1 is shown as normally driving the clutch member 2 through an extending hollow framework 3| andsleeve 32, the latter journaled in the fixed frame 29'at its forward end. The sleeve 32 is shown as driving an intermediate clutch member 33 through splines 34. Between the members 33 and 2 there is shown one-way or overruning clutch 35, the jaw teeth being normally held together by a compression spring 36 which is shown as placed around the shaft 31, said shaft being secured at its forward end to clutch 2. Said spring is shown as bearing at one end against the rear of clutch 33 and at its other end' against a collar 43 on the shaft 31.

I now come to themechanism for quickly bringing the main jaw teeth of clutches I and 2 into engagement. This preferably comprises a second electric motor 38, preferably having a small armature 39 of small inertia and wound for relatively low speed. The shaft 40 of said armature is shown as journaled at its rear end within the sleeve 9. The forward end of said shaft is provided with a collar 54 which may act as a bearing in an intermediate sleeve 53 within the sleeve 32. The field of said-motor may be mounted within the extension 3| of. housing l0 so as to rotate with the same, although this is not necessary and might be avoided by mounting the motor in a different position. Said collar 54 is also shown as having a plurality of cam surfaces or teeth 4| adapted to engage, upon rotation of the armature, cooperating cam surfaces 42 within the collar" so as to force the latter collar to the left upon relative rotation of the armature, against the action of compression spring 44, and bring the jaws l and 2 into prompt engagement, At the same time spring 36 pushes 33 forward to-keep teeth 35 in engagement. At the same time, the upper edge of teeth 4lwill engage the lower edges of the teeth 45 on the collar 43 to rotate the shaft 31 through a sumcient angle to bring the heavy jaw teeth on 2 into torsional engagement with the jaw teeth on I.

This will obviously occur very quicklyv on account of the low inertia of the armature 39 and the fact that no gear reductions are employed. As soon, however, as the jaw teeth are in engagement, the armature 39 will rotate at the same slow speed as the housing 10 and jaw 2 while, on the other hand, the high speed shaft 8 of the motor 4 will continue to rotate at high speed to drive the clutches through the large reduction gearing.

By employing separate electric motors for causl, ing the clutch engagement and for supplying the power to rotate the clutch after engagement, I

not only avoid the difficulties of the prior art construction, but my construction is susceptible of causing the clutch engagement materially ahead of the cranking operation, if desired. This may easily be accomplished by employing separate starting contacts 56 and 51 for the two motors on the starter pedal 58, the contact 56, operating the engaging motor 38, being closed momentarily ahead .of the contact 51, operating the cranking motor. Obviously, however, this precaution may not be necessary and the two motors may be operated from one contact in most cases.

It should also be noted that when the engine itself starts and rapidly accelerates, the main jaw teeth will stay in axial and rotational engagement due to motor 39 as long as the starting pedal is down, so that in case the engine dies again, cranking will be resumed with no lost motion or shock.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter containedin the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In an electric starter for combustion engines, an engine engaging member, 'a main electric motor, reduction gearing connecting said motor and member to rotate said member slowly with large available torque, an auxiliary relatively small electric motor of low torque, both said motors being energized during the starting operation, and mechanism operated solely by cal-:1 auxiliary motor for advancing said. member into engagement with the engine.

2. In an electric starter for combustion engines, an engine engaging jaw clutch, a main electric motor, reduction gearing connecting said motor and-clutch to rotate said clutch slowly with large available torque, an auxiliary electric motor,

and mechanism operated thereby for advancing l said clutch into engagement with the engine both axially and rotationally.

3. An electric starter as claimed in claim 1, in

a which the said main motor and auxiliary motor and member to rotate said member slowly with large available torque, an auxiliary electric motor of insuiiicient power to crank the engine, mechanism directly operated thereby for advancing said member into engagement with the engine, and means for bringing the auxiliary motor into action ahead of the main motor.

6. In an electric starter, a jaw clutch adapted to be advanced into engagement with the engine,

an electric motor, a lost' motion connection be-' tween said motor and clutch adapted to first advance said clutch into engagement with the engine and then exert some starting torque thereon, a separate motor, reduction gearing connecting said motor and clutch to exert an additional starting torque on said clutch, and an overrunning clutch between the drives from the two motors.

7. In an electric starter for combustion engines, an engine engaging member, a main electric motor, reduction gearing connecting said motor and member to rotate said member slowly with large available torque, an overrunning clutch between said member and motor, an auxiliary electric motor directly connected to said member, both said motors being energized during the starting operation, and mechanism operated by said auxiliary motor for advancing said member into engagement with the engine.

8. In an electric starter, a main and an auxiliary electric motor, reduction gearing connected to the former, an engine engaging jaw clutch member of relatively few large teeth positively driven .by said gearing and adapted to engage a complementary jaw member on the engine, an overrunning clutch having relatively many small teeth between said first named jaw and said main motor, and a direct connection between said auxiliary motor and said jaw to' cause said jaw to keep up 'with the engine during sudden acceleration of said complementary jaw on the latter.

ALBERT S. FISK. 

